1. Field of the Invention
The invention relates to an indexing device for a data storage system, and more particularly, to an indexing device for rapidly indexing an input/output (I/O) descriptor.
2. Description of the Prior Art
The amount of digital data nowadays is getting bigger and bigger that's why the data storage system capable of storing large amount of digital datum is taken seriously. The Serial Attached Small computer system interface (SAS) data storage system can comprise a plurality of data storage devices to increase the capacity of data storage system, or further enhancing its efficiency and security with Redundant Array of Independent Drives (RAID).
In additional, the SAS data storage system can be used in compliance with SAS data storage device and Serial Advanced Technology Attachment (SATA) data storage device, so as to increase its extension and selectivity more flexibly.
When a host device sends a host I/O command to a controller of the SAS data storage system, the controller, according to the host I/O command, generates I/O descriptors respectively corresponding to the data storage devices. According to the I/O descriptors, the controller generates I/O commands and then transmits the I/O commands to the data storage devices correspondingly. After executing the I/O command, the data storage device transmits an I/O response corresponding to the I/O command to the controller, so as to execute the following I/O processing procedures, such as Direct Memory Access (DMA), and so on. At the same time, the controller must retrieve the I/O descriptor corresponding to the I/O response, so as to execute the following I/O processing procedures based on the I/O descriptor.
However, the SAS data storage system can comprise a plurality of data storage devices, and some data storage devices can buffer a plurality of queued I/O commands. Therefore, the controller can transmit a lot of I/O commands within a short time. For this reason, when the controller receives an I/O response from the data storage device and retrieves the I/O descriptor corresponding to the I/O response, a fast and efficient indexing method is required to ensure the process efficiency of the system. However, the SAS standard does not provide the indexing method for retrieving the I/O descriptor corresponding to the I/O response.
Accordingly, the main scope of the invention is to provide an indexing device and method for a data storage system to solve the aforementioned problems.